<template>
<div>
  <div class="goods">
    <div class="menu-wrapper" ref="menuWrapper">
      <!-- 菜单对应的是食物分类列表-->
      <ul>
        <!--current 是标识当前分类的class 而它的值应该是一个计算后的布尔值-->
        <li
          class="menu-item"
          v-for="(good, index) in goods"
          :class="{ current: index === currentIndex }"
          @click="clickMenuItem(index)"
          :key="index"
        >
          <span class="text bottom-border-1px">
            <img class="icon" :src="good.icon" v-if="good.icon" />
            {{ good.name }}
          </span>
        </li>
      </ul>
    </div>
    <div class="foods-wrapper" ref="foodsWrapper">
      <!-- 右侧的食物列表是根据左侧的分类列表展现的-->
      <!-- 所以右侧是在一个分类标题列表里面嵌套着各类食物列表-->
      <ul ref="foodsUl">
        <li class="food-list-hook" v-for="(good, index) in goods" :key="index">
          <h1 class="title">{{ good.name }}</h1>
          <ul>
            <li
              class="food-item bottom-border-1px"
              v-for="(food, index) in good.foods"
              :key="index"
              @click="showFood(food)"
            >
              <div class="icon">
                <img width="57" height="57" :src="food.icon" />
              </div>
              <div class="content">
                <h2 class="name">{{ food.name }}</h2>
                <p class="desc">{{ food.description }}</p>
                <div class="extra">
                  <span class="count">月售{{ food.sellCount }}份</span>
                  <span>好评率{{ food.rating }}%</span>
                </div>
                <div class="price">
                  <span class="now">￥{{ food.price }}</span>
                  <span class="old" v-if="food.oldPrice"
                    >￥{{ food.oldPrice }}</span
                  >
                </div>
                <div class="cartcontrol-wrapper">
                  <CartControl :food="food" />
                </div>
              </div>
            </li>
          </ul>
        </li>
      </ul>
    </div>
    <ShopCart />
  </div>
  <Food :food="food" ref="food"/>
</div>
</template>

<script>
import { mapState } from 'vuex'
import BScroll from 'better-scroll'
import CartControl from '@/components/CartControl/CartControl'
import Food from '@/components/Food/Food'
import ShopCart from '@/components/ShopCart/ShopCart'

export default {
  data () {
    return {
      scrollY: 0, // 右侧 Y 轴滑动的坐标(越往下数值越小)
      tops: [], // 包含右侧所有分类小列表的 top 值
      food: {} // 需要显示的food
    }
  },
  // （参考12.2解决swiper的bug，之前使用watch和nextTick来监听数据更新）

  // 要考虑列表显示之后创建BScroll实例的时机
  // 这里使用另一种方法 通过action的回调函数来通知组件数据已经更新
  mounted () {
    // 使用 axios 请求 mockjs 提供的接口
    this.$store.dispatch('getShopGoods', () => { // 数据更新后执行
      this.$nextTick(() => { // 列表数据更新显示后执行
        this._initScroll()
        this._initTops()
      })
    })
  },
  computed: {
    ...mapState(['goods']),

    // 计算当前分类的下标
    // eslint-disable-next-line vue/return-in-computed-property
    currentIndex () { // 初始和相关数据发生了变化
      // 得到相关的条件数据
      const { scrollY, tops } = this
      // 根据条件计算产生一个结果
      const index = tops.findIndex((top, index) => {
        // scrollY >= top && scrollY < 下一个top
        return scrollY >= top && scrollY < tops[index + 1]
      })
      // 返回结果
      return index
    }
  },
  methods: {
    _initScroll () { // 初始化滚动条
      /* eslint-disable no-new */
      if (!this.scroll) {
        new BScroll('.menu-wrapper', {
          click: true
        })
        this.foodsScroll = new BScroll('.foods-wrapper', {
          probeType: 2, // 因为惯性滑动不会触发
          click: true
        })
      }
      // 给右侧列表绑定scroll 监听
      this.foodsScroll.on('scroll', ({ x, y }) => {
        // console.log(x, y)
        this.scrollY = Math.abs(y)
      })
      // 给右侧列表绑定scroll 结束监听
      this.foodsScroll.on('scrollEnd', ({ x, y }) => {
        console.log(x, y)
        this.scrollY = Math.abs(y)
      })
    },
    _initTops () { // 收集top值
    // 初始化tops
      const tops = []
      let top = 0
      tops.push(top)
      // 找到所有分类的li
      const lis = this.$refs.foodsUl.getElementsByClassName('food-list-hook')
      Array.prototype.slice.call(lis).forEach(li => {
        top += li.clientHeight
        tops.push(top)
      })
      // 更新数据
      this.tops = tops
    //   console.log(tops)
    },
    // 左侧点击 右侧滑动事件
    clickMenuItem (index) {
      //   console.log(index)
      // 是右侧列表滑动到对应的位置
      // 得到目标位置scrollY
      const scrollY = this.tops[index]
      // 立即更新scrollY(让点击的分类项成为当前分类)
      this.scrollY = scrollY
      // 右侧滑动
      this.foodsScroll.scrollTo(0, -scrollY, 300)
    },
    // 显示点击的food
    showFood (food) {
      // 设置food
      this.food = food
      // 显示food  (父组件调用子组件对象的方法)
      this.$refs.food.toggleShow()
    }
  },
  components: {
    CartControl,
    Food,
    ShopCart
  }
}
</script>

<style lang="less" scoped>
.goods{
    display: flex;
    position: absolute;
    top: 195px;
    bottom: 46px;
    width: 100%;
    background: #fff;
    overflow: hidden;
    .menu-wrapper{
      flex: 0 0 80px;
      width: 80px;
      background: #f3f5f7;
      .menu-item{
        display: table;
        height: 60px;
        width: 56px;
        padding: 0 12px;
        line-height: 14px;
        &.current{
          position: relative;
          z-index: 10;
          margin-top: -1px;
          background: #fff;
          color: #1989fa;
          font-weight: 700;
          .text{
            border:none;
            }
        }
        .icon{
          display: inline-block;
          vertical-align: top;
          width: 12px;
          height: 12px;
          color: #1989fa;
          margin-right: 2px;
          background-size: 12px 12px;
          background-repeat: no-repeat;
        }
        .text{
          display: table-cell;
          width: 56px;
          vertical-align: middle;
          border-bottom:1px solid rgba(7, 17, 27, 0.1);
          font-size: 12px;
        }
       }
    }
    .foods-wrapper{
      flex: 1;
      .title{
        padding-left: 14px;
        height: 26px;
        line-height: 26px;
        border-left: 2px solid #d9dde1;
        font-size: 12px;
        color: rgb(147, 153, 159);
        background: #f3f5f7;
      }
      .food-item{
        display: flex;
        position: relative;
        margin: 18px;
        padding-bottom: 18px;
        border-bottom:1px solid rgba(7, 17, 27, 0.1);
        &:last-child{
          border: none;
          margin-bottom: 0;
        }
        .icon{
          flex: 0 0 57px;
          margin-right: 10px;
        }
        .content{
          flex: 1;
          .name{
            margin: 2px 0 8px 0;
            height: 14px;
            line-height: 14px;
            font-size: 14px;
            color: rgb(7, 17, 27);
          }
          .desc,.extra{
            line-height: 10px;
            font-size: 10px;
            color: rgb(147, 153, 159);
          }
          .desc{
            line-height: 12px;
            margin-bottom: 8px;
          }
          .extra{
            .count{
              margin-right: 12px;
            }
          }
          .price{
            font-weight: 700;
            line-height: 24px;
            .now{
              margin-right: 8px;
              font-size: 14px;
              color: rgb(240, 20, 20);
            }
            .old{
              text-decoration: line-through;
              font-size: 10px;
              color: rgb(147, 153, 159);
            }
          }
          .cartcontrol-wrapper{
            position: absolute;
            right: 0;
            bottom: 12px;
          }
         }
        }
    }
}
</style>
